I hope you were being sarcastic. If not...The question is why should the government be involved with the licensing of marriages at all. Implicit with the power to confer any license is the power to deny said license.
Because the gov't has an interest in promoting certain kinds of relationships over other kinds of relationships. This is so because certain kinds of relationships tend to produce better citizens than others.
and I'll reiterate that fags have the same rights to marry as anyone else.
What sort of bullshit are you talking about? Since when has denying marriage licenses kept people from procreating without one? Taking your logic to it's ultimate conclusion it would also be in the governments interest to force sterilizations on those they deem unfit to have children. Or perhaps take away their breathing licenses.